Emms S K, Stratton D A, Snow A A
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, New Jersey, 08544-1003.
Department of Plant Biology, Ohio State University, 1735 Neil Avenue, Columbus, Ohio, 43210-1293.
Evolution. 1997 Oct;51(5):1481-1489. doi: 10.1111/j.1558-5646.1997.tb01471.x.
We studied the relationship between inflorescence size and male fitness in the andromonoecious lily Zigadenus paniculatus, using experimentally manipulated inflorescences to eliminate possible correlations between flower number, resource availability, and other floral traits. Allozyme markers were used to determine the siring success of large versus small plants in 14 arrays of plants, each array containing five large and five small plants. The inflorescence size of small plants was held constant both within and among arrays; the size of large plants was held constant within an array but was varied among arrays. Large plants sired more than half the seeds in 12 of the 14 arrays, and significantly more than half in six of these 12. However, in eight of the arrays, large plants sired significantly fewer seeds than expected on the basis of their size advantage. Furthermore, there was no significant relationship between relative size and relative siring success in comparisons among arrays. A maximum-likelihood model estimated that 28% of seeds were sired by imported pollen, with 95% confidence limits of 13% and 50%. Within these limits, high import rates tended to mask the relative success of large plants in several arrays. These results suggest that the evolution of inflorescence size in Z. paniculatus is at least partly driven by selection for increased male success, assuming genetic variation for flower number. However, the data also support a growing body of evidence that estimates of male fitness in plants can be highly variable. We discuss the sources of this variability and the possible effects of inflorescence design on the relationship between inflorescence size and fitness.
我们研究了雄花两性同株的垂花棋盘花（Zigadenus paniculatus）中花序大小与雄性适合度之间的关系，通过对花序进行实验操作，以消除花数量、资源可用性和其他花部性状之间可能存在的相关性。利用等位酶标记来确定14组植株中大型植株和小型植株的父本成功情况，每组包含五株大型植株和五株小型植株。小型植株的花序大小在组内和组间均保持恒定；大型植株的大小在组内保持恒定，但在组间有所变化。在14组中的12组里，大型植株产生了超过一半的种子，其中6组显著超过一半。然而，在8组中，大型植株产生的种子数量比基于其大小优势预期的要少得多。此外，在组间比较中，相对大小与相对父本成功之间没有显著关系。一个最大似然模型估计，28%的种子是由外来花粉产生的，95%的置信区间为13%至50%。在这些范围内，高外来花粉率往往掩盖了大型植株在几组中的相对成功情况。这些结果表明，假设花数量存在遗传变异，垂花棋盘花花序大小的进化至少部分是由增加雄性成功的选择驱动的。然而，这些数据也支持了越来越多的证据，即植物中雄性适合度的估计可能高度可变。我们讨论了这种变异性的来源以及花序设计对花序大小与适合度之间关系的可能影响。
